


Part of His World

by GuixonLove



Category: Sherlock (TV)
Genre: Alternate Universe - Fantasy, Johnlock Roulette, Kid Fic, M/M, Mer!John
Language: English
Status: Completed
Published: 2016-07-11
Updated: 2016-07-11
Packaged: 2018-07-23 00:54:20
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,800
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7460313
Author URL: https://archiveofourown.org/users/GuixonLove/pseuds/GuixonLove
Summary: <blockquote class="userstuff">
              <p>As a child, Sherlock and his family go on a holiday to a beach where something happens: he makes a friend.</p>
            </blockquote>





	1. A Fateful Meeting

**Author's Note:**

> Check out the gorgeous artwork based on this fic!  
> practicefortheheart: [one](http://practicefortheheart.tumblr.com/post/78690942038/guixonlove-time-seemed-to-fly-by-as-they) and [two](http://practicefortheheart.tumblr.com/post/84358806619/guixonlove-what-is-it-john-he-asked-did-i)  
> shootbadcabbies: [one](http://shootbadcabbies.tumblr.com/post/97673671364/guixonlove-my-commission-from-shootbadcabbies)

Sherlock Holmes kicked at a pile of seaweed as he wandered along the edge of the beach, trying to get away from his older brother Mycroft. He scowled. Mycroft had just given him a speech about how he needed to grow up and stop being so childish. Sherlock scoffed at the memory, and shook his unruly curls out of his eyes as he continued walking. What did Mycroft know, anyway? From what Sherlock could tell, being a grown-up wasn’t all that great, and he was in no hurry to become anything like his stuffy older brother. If he had his way, he would run away and become a pirate. He would go on adventures every single day, looking for buried treasure, and not have to listen to anyone but himself. 

Sherlock smiled at the thought and brought his foot up to kick at another pile of seaweed. A flash of white in the sand caught his eye. He knelt down and dug in the sand, uncovering a seashell that looked as though it had been snapped in half before it had washed ashore. Sherlock gently picked it up and studied it closely. It was round and pearlescent white; the surface had been worn smooth over time while the bottom edge was jagged where it had been broken. He stood, slipping the shell into his pocket, and continued to walk along the waterline when he heard a loud splash coming from somewhere further up the beach. He looked around at his surroundings and saw nothing but sand and sea. 

Sherlock wandered along the beach for a while, walking along the curve in the shoreline, before he came across a little cavern. He paused and looked back to where he had just walked. He bit his lip, feeling torn as his eyes kept drifting back to the cave. When he heard another splash coming from inside the cavern, he made up his mind and began to quickly walk towards it. 

He peered inside, the sun filtering in dimly through a few gaps in the top of the cavern, making the water glitter a deep blue where the light hit it. A boy was floating in the shallow water and sorting through a pile of seashells on the sand. Sherlock stepped further into the cave to get a closer look, hiding behind a large rock near the entrance and staring at the boy in the water. He watched with rapt interest as the boy picked up and examined different seashells from the pile in front of him, placing the ones he liked in a little bag that lay on the sand next to him and tossing the ones he didn’t back into the ocean. 

The boy looked to be around Sherlock’s age, maybe a little older. His short blonde hair was sticking up in different directions and dripping water down his tanned face and torso. Sherlock could also make out some form of markings which looked like silvery tattoos on the boy’s neck. The boy used his upper body to push himself up onto the sand to reach a shell that had rolled away and that was when Sherlock saw it. The boy had a long fish tail where his legs should have been, which slapped at the water in glee when he found a shell he liked. Sherlock gasped softly and tried to get a closer look at the tail when he slipped, knocking a few loose rocks over, the sound echoing in the cavern. The boy started, his eyes widening in fear as they darted around the cave.

“Who’s there?” he asked tentatively, picking up a seashell and looking as if he had every intention of throwing it. “I’m not afraid of you, whoever you are. I have a weapon and I will use it.”

“Sorry,” Sherlock said as he walked out from behind the rock, holding his hands up apologetically. “I didn’t mean to scare you.” He continued to tiptoe cautiously over to the edge where the sand met the ocean, keeping his hands raised to show that he meant him no harm. The boy slowly lowered the shell in his hand and stared at Sherlock warily. Sherlock knelt down in front of the boy and they stared at each other in wonder and curiosity. Now that he was closer, Sherlock could see that the silver markings on the boy’s neck were actually gills. “Remarkable,” he murmured.

The boy cocked his head in confusion. “What is?”

“You are,” Sherlock breathed, his eyes wide in awe and astonishment. “I’ve only read about creatures like you in books. I’ve always thought they were only fairy tales and not real.”

“Well, as you can see, I am quite real,” the boy replied. He paused, and looked at Sherlock curiously. “There are stories about me?”

“Not about you specifically. They’re about your kind in general,” Sherlock replied, waving his hand dismissively. “That’s not important though. Will you sit up here so I can see your tail… please?” he asked bluntly, adding the please as an afterthought.

“Why?” the boy asked, his eyes narrowing. “Is this some kind of trick where you try to capture me as soon as I get out of the water?”

Sherlock gaped at the boy in surprise. “Why would I do that? Is that what people normally do when they ask to see your tail?”

The boy shrugged and looked down at the pile of shells in front of him, picking one up and turning it over in his hand. “I don’t actually know. I mean, I’ve heard stories about humans from my parents. They have talked to other Mers who have encountered them but I’ve never actually seen one, let alone talked to one before.” He looked back up and met Sherlock’s eyes. “Are you going to hurt me?” He asked, deep blue eyes wide with anxiety. 

Sherlock felt his heart drop to his stomach. How many times had he asked that same question to the other children he went to school with? He couldn’t imagine hurting anyone, let alone someone as fascinating as the boy in front of him. “I won’t hurt you, I promise.”

The boy stared at Sherlock hesitantly for a couple of seconds before he relaxed, the tension slowly leaving his muscles. “My name’s John. What’s yours?”

“Sherlock,” he replied. John giggled, the sound settling warm in Sherlock’s chest. “What’s so funny?”

“Your name,” John said. “I’ve never heard of anyone called ‘Sherlock’ before.” He continued to giggle as he pulled himself out of the water and sat down next to Sherlock on the sand. “I like it.”

“Well, you’d be the only one,” Sherlock replied with a frown as he thought of all the taunts he usually received when he was at school. He turned until he was facing John so he could inspect his tail closely. It was a lovely shade of aquamarine that reminded him of his mother’s favorite necklace. The scales appeared to shimmer as they reflected the scant amount of light that was shining into the tiny cave. He lifted a hand to touch but paused and glanced up at John who was staring at him, his eyes inquisitive. “May I?”

John nodded, so Sherlock reached forward and gently ran his fingers over the blue scales. The tail felt smooth and was cool and slippery to the touch. He wondered to himself what a scale would look like under his microscope back home, but quickly shook the thought from his head. His eyes wandered up to John’s torso, noting where scales lightened and gradually became skin, and down to the fin and watched as it flicked and sent droplets of water flying. Sherlock felt a strange pull towards John, as if something wanted him to get closer and never leave him. He remembered the feeling in his gut that told him to go into the cave to begin with.

“You are, without a doubt, one of the most interesting people I have ever met,” Sherlock said softly. 

John glanced at him curiously. “Why? Because I have a tail?” 

Sherlock shook his head. “No, it’s not that,” he said as he brought his eyes up and met John’s. “I mean, that’s really interesting too, but...I don’t know, I feel like something wanted me to come into this cave to find you.” He paused and looked down at his hands briefly before looking back up at John. “Sorry, that was stupid. My older brother always tells me I need to learn to think before I speak.” He pointed at the bag laying on the sand between them. “Did you find any interesting shells?”

John tilted his head and shot Sherlock a confused glance before he picked up the bag and began to show him all of the shells he found. Time seemed to fly by as they studied the shells together and made each other laugh. Sherlock couldn’t remember the last time anyone who wasn’t family spent that much time with him and actually enjoyed themselves. The warm feeling in his chest seemed to grow stronger with each passing minute and it made Sherlock want to feel this way forever. John looked at Sherlock, his eyes shining happily, and reached into his bag again.

“This last one is definitely my favorite,” John said ecstatically as he reached into the bag and pulled out a shell that was strangely similar to the one Sherlock had found on the beach earlier. “This was the first shell I found before I decided to come into this cavern to look for more!”

Sherlock sat in stunned silence as he stared at the shell in John’s hand. John’s smile slowly disappeared and changed into a look of concern. 

“Sherlock? Are you okay?”

Sherlock nodded. “Yeah, I’m fine. It’s just that that shell looks like the one I found on the beach!” he explained. John grinned.

“Really? Can I see?” he asked excitedly. Sherlock reached into his pocket to pull out the shell when he heard a voice outside of the cave.

“Sherlock! Where are you, brother mine?”

Sherlock rolled his eyes and looked at John who was quickly throwing his shells back into his bag. “It’s just my brother, Mycroft,” he explained. “He won’t hurt you, I won’t let him.”

John looked at Sherlock and smiled. “I know that,” he said as he slipped his bag over his shoulder. “I trust you, Sherlock. I should probably be headed back home myself anyway.”

Sherlock grinned back and stood up, brushing the sand off of his trousers. “Do you think I could see you again?” he asked expectantly. John nodded as he slid back into the water. 

“Let’s meet back here tomorrow,” John said, as he floated in the water looking up at Sherlock. “And bring that shell you were going to show me.” With that, John slipped under the surface and disappeared from view. Sherlock smiled to himself and ran out of the cave to tell Mycroft about his new friend. 

The next day, Sherlock woke up to the sun shining brightly through his window. He lay in bed and recalled the events of the previous afternoon. He had told Mycroft about John but Mycroft had been convinced that Sherlock had been in the sun for too long and had imagined the whole thing. Sherlock frowned briefly before he remembered that he was going to see John again which made him grin instead. He sat up and picked up the shell he found yesterday off the nightstand, and turned it over in his hand. He was contemplating what he and John could do today when there was a knock on his door, and his mother came in, looking a bit flustered. 

“Oh good, you’re awake, Sherlock! You need to hurry and get dressed because the taxi will be here shortly to take us home today.”

Sherlock frowned. “No, we weren’t leaving until tomorrow.” His mother smiled sadly and brushed the curls out of his eyes.

“I know, but your father was needed back in town so we’re going to have to cut our vacation short,” she replied. She kissed his forehead and stood up. “We can come back again next year, I promise. Now, let’s get you dressed so we can go.”

Sherlock nodded numbly and watched as his mother flitted around the room, picking up his clothes and putting them into his suitcase and setting out an outfit for him to wear on the way home. He looked out of the window and fought back tears, hoping that John wouldn’t be too upset with him for not meeting him today, and that he wouldn’t lose the only friend he’d ever had.


	2. A Joyful Reunion

**Summary for the Chapter:**

> Years later, Sherlock returns to the beach, hoping to find what he lost.

Sherlock paid the driver and stepped out of the taxi, taking a deep breath of the salty air. It had been twelve years since he had last been on this beach, and the thought caused the ache in his chest to grow. A few months after that vacation, his father got sick and passed away, so his mother had sold the beach house. Whenever Sherlock asked her if they could go back, she just sighed and told him it was too hard for her. Sherlock slid his hand into his coat pocket and pulled out the seashell he had found the day he met John. He had held onto it all of these years because it reminded him of the one and only friend he had ever made. Anytime he was upset, he would pick up the shell and stare at it for hours, remembering John and feeling a warmth that spread throughout his chest whenever he thought of him. He often wondered if John ever thought of him or if he even remembered him. Many years had passed since that day at the beach and Sherlock still had that reaction whenever he thought of John. He had asked his mother once what that feeling was and she had told him that it sounded like he was in love. Later that night, he had dreamt of John. They were swimming together, and he had a tail, just like John’s, except his was a silvery blue. When he woke up, he had thought he saw the shell glowing on his nightstand. He had picked it up and felt the pull to go back to the beach. When his mother died a few years ago, it had seemed like that shell and the memory of John were the only things that were keeping him from breaking into a million pieces.

Sherlock was spending his winter break back home in an empty house, since Mycroft was off somewhere being the British government, and he was trying to stave off boredom when he felt the sudden urge to return to the beach. He tried to ignore it but the feeling continued to nag at him until he got fed up, packed a bag and made the two and a half hour trip to the beach. He sighed, slipping the shell back into his pocket, and began his trek across the sand to the little cavern where he and John had met. 

He entered the dimly lit cave and saw a young man with blonde hair sitting on the sand, turning a shell over in his hands and staring at the water. Sherlock blinked a few times and realized the man had an aquamarine colored tail, the same exact color of the one that he often saw in his dreams. 

“John?” He asked timidly, not sure if he was really seeing him, or if his eyes were deceiving him. The man looked up in surprise and let out a gasp.

“Sherlock? Is that really you?” John asked in disbelief. Sherlock walked further into the cave and dropped to his knees beside John. 

“Yeah, it’s me,” he replied sheepishly. “Sorry, I’m late. I-” Sherlock was cut off when John threw his arms around him and hugged him tightly. He sat stunned for a moment before he wrapped his arms around John and hugged him back. He buried his nose in John’s neck and sighed happily. They pulled away after a few minutes and studied how much the other had changed over the years. Sherlock’s eyes drifted down from John’s face and noticed a scar on his left shoulder that wasn’t there when they first met. He brought a hand up and gently ran his fingers over the raised skin. 

“A fisherman threw a spear at me a couple of years ago,” John said quietly, answering Sherlock’s unspoken question. He looked down at the shell in his hands briefly before he met Sherlock’s eyes. “What happened to you, Sherlock? I waited for you all day and you never came back.”

Sherlock swallowed hard against the lump that had formed in his throat. He sat down on the sand and watched the waves lap gently against John’s tail. “I know. My family had to go back home and I had no choice but to go with them.” He glanced up and met John’s eyes before continuing, his voice starting to break. “But I never forgot about you. You were the only friend I’ve ever had. I held onto the shell I found that day and it always made me feel better because it reminded me of you.” Sherlock reached into his pocket and pulled out the shell to show to John when he heard him gasp. He looked down and saw that the shells they were both holding were glowing softly. 

“I thought it was just an old mertale,” John murmured. He gently took the shell Sherlock was holding and put it with his own shell, where they fit together perfectly. Sherlock looked from the two shells and back at John expectantly, waiting for an explanation. John continued, “The story goes that if two people find two halves of a shell that fit together perfectly, it means they’ve found their soulmate. I never knew that it was more than just a story.” 

Sherlock stared at John, completely flabbergasted as he absorbed the information he just received. “Do you think that’s why we both felt like we needed to explore this cave the day we met and why we felt like we needed to come back?” he inquired.

“I don’t know,” John admitted before shrugging. “But now that I think about it, it makes sense.” 

“What do you mean?” Sherlock asked, a slight frown on his face. 

“You said that when you were sad looking at the shell made you feel better, right? Well, my shell did the same thing for me when I got this,” John explained, pointing at the scar on his shoulder. “I’ve thought about you so much over the years, Sherlock. I always wondered if something happened to you and that’s why you never came back, but something inside of me knew that you would come back to me someday.” He looked up and met Sherlock’s gaze. “And it looks like I was right.”

Sherlock brought his hand up and cupped John’s face gently, then leaned forward and brushed his lips softly against John’s. John gasped in surprise, his hands coming up to rest on Sherlock’s shoulders and returned the kiss. Sherlock pulled away and rested his forehead against John’s, his eyes closed. “I love you,” John whispered softly. Sherlock’s eyes snapped open as he sat back so he could look at John in disbelief. 

“What did you say?” He asked. John’s face reddened and he tried to look away but Sherlock’s hands on his face stopped him. He slowly met Sherlock’s icy blue eyes, which appeared to be filled with unshed tears. “Would you say it again? Because no one besides my parents has ever said that to me before and I’ve wanted to hear it from you for so long. Please, John?” Sherlock pleaded. John leaned forward until their heads were touching again, his eyes never leaving Sherlock’s.

“I love you, Sherlock,” he said. Sherlock’s eyes closed as he committed the sound of John’s confession to memory, filing it away so he could always remember it. He opened his eyes and smiled at John.

“I love you too, John. I think I have since the day we met when we were children.” John smiled brightly at this, and then leaned in and captured Sherlock’s lips again. Sherlock slid his tongue along the seam of John’s lips, tasting salt from the ocean. He felt John’s thumbs grazing his neck when, all of a sudden, John jerked away from him. Sherlock opened his eyes and saw John staring at him in shock. 

“What is it, John?” he asked. “Did I do something wrong?” John opened and closed his mouth a few times before he found the ability to speak. 

“No! It’s not that. It’s just… you… Sherlock, you have gills and a tail now,” John managed to choke out. Sherlock looked down and saw that his legs were gone and in their place was a silvery blue tail, just like he had in his dreams all those years ago. He brought his hands up to his neck and felt slits instead of flesh. Sherlock met John’s eyes.

“How did this happen, John?” he asked, trying his best to remain calm. John looked just as confused as he felt. He opened his mouth to speak when his eyes landed on the shells laying on the ground beside them. Sherlock followed his gaze and saw that the shells were glowing even brighter than before. “Was this ever in those stories you were told when you were a child?”

“I...I don’t remember. I don’t remember hearing what would happen if this happened between a mer and a human,” John said. He looked at Sherlock apologetically. “I’m so sorry, Sherlock. I can try to find out if there’s a way to change you back so you can go back to your family...” Sherlock cut him off with a kiss. He pulled away and pressed a kiss to John’s forehead.

“I don’t have a family to go back to. Both of my parents died and my older brother is hardly ever home and when he is, he pays no attention to me,” he explained. “You’re the only one I want to be with. That is, if you even still want me.” John chuckled softly and pulled him into a tight hug. 

“Of course I still want you,” he murmured into Sherlock’s ear, his hands running up and down Sherlock’s back. John sat back and grinned at Sherlock before he grabbed their shells and slid into the water. “Come on, let’s go home.” Sherlock smiled as he took his coat and shirt off and eased himself into the water. He grabbed John’s hand and they slipped under the surface and began their swim home together.

**Notes for the Chapter:**

> Find me on Twitter and Tumblr as GuixonLove87

**Author's Note:**

> Find me on Twitter and Tumblr as GuixonLove87


End file.
